This invention relates to guides for use in guiding piles during pitching in interlocking sheet piling.
In such piling, a pile to be pitched is lifted up by a crane to above the level of the adjacent already pitched pile and the adjoining lateral edge portions of the piles must be precisely aligned so that on lowering the pile being pitched said lateral edge portions of the two piles are interlocked. This has been done by having a man stationed at the top of the previously pitched pile to guide the pile being pitched manually into position, but that is a difficult and dangerous operation, particularly in windy conditions, and in bad weather it becomes impossible.
Accordingly various forms of guide apparatus have been devised to enable the guiding of piles to be carried out without the need for having a man in this exposed and dangerous position. Examples of such known guides are to be found in U.S. Pat. Nos. 2,161,482, 2,583,928, 2,833,119, 2,968,931 and 4,028,901, and U.K. Pat. No. 1,483,188, but these have a number of disadvantages.
For example, these guides are not easily attachable to the two piles. With the guides of U.S. Pat. Nos. 2,161,482 and 2,833,119 it is necessary to drill holes in the piles to attach them, while the guide of U.S. Pat. No. 2,583,928 must be secured to both piles simultaneously, which can be difficult or impossible in adverse conditions. With the guide of U.S. Pat. No. 2,968,931, clamping to the already pitched pile requires a complicated procedure including the separate securing of two different parts either of which may therefore be overstrained before the pile has been properly engaged. The guides of U.S. Pat. No. 4,028,901 must first be placed at the top of a pitched pile so that a crane must be employed to place the guide in position which requires the exercise of considerable skill and is also made more difficult by adverse weather conditions.
These known guides also have deficiencies in the guidance they offer. Generally, sliding engagement faces are provided in order to locate the two piles satisfactorily in the required relative orientation, but as a result the function of the guides can be seriously impaired, for example due to dimensional variations or due to increased bearing pressure resulting from high wind loads. These sliding engagements can also jam if the pile to be pitched is skewed due to careless handling.
In U.S. Pat. No. 2,583,928, where the section of the pitch pile has a lobed interlock edge, a pair of rollers engage the reduced thickness of the edge immediately behind said lobe, but they offer little support against relative pivoting movement between the piles about a vertical axis. In U.S. Pat. No. 4,028,901 there is positive guidance of the pile being pitched by means of a series of rollers connected in a template-like device, but this requires a relatively massive structure, which, as already mentioned, must be fixed to the top of the already pitched pile.
On the question of attachment of the guides, since the principle of operating at ground level requires the guide to be fixed to the bottom of the pile to be pitched while it is drawn up the side of the already pitched pile, it is also desirable to ensure that the guide is securely fixed to the pile to be pitched so that any increase of resistance to movement along the other pile will not dislodge the guide and leave it out of alignment. This condition is difficult to satisfy if the guide is only frictionally held and is satisfied in the known guide only by drilling attachment holes at the bottom of the piles to be pitched.